Somaclonal variation in the progeny of plants regenerated from callus cultures of seven inbred lines of maize

Abstract

Callus cultures were initiated from immature embryos of three dent corn inbred lines: FR27rhm (B73 derivative), 79-R4443, and EXL1; and four sweet corn (sh-2) inbred lines: f84-267, f84-275, f84-278, and f84-700. Extensive qualitative variation was noted in self-pollinated progeny of plants regenerated from callus of FR27rhm, EXL1, and f84-700; quantitative variation was measured in self-pollinated progeny of plants regenerated from cultures of almost all inbreds. Most qualitative mutations were visible in the first self-pollinated generation; chimerism in regenerated plants was indicated by initial segregation of some mutants after two self-pollinations. All culture-induced mutant phenotypes were similar to known spontaneous mutations in maize; preliminary data indicate most have single-gene recessive inheritance. For qualitative variation, average mutation frequencies per regenerated plant were calculated as 0.18, 0.71, and 0.64 for FR27rhm, EXL1, and f84-700, respectively. Differences in mutation frequency among the four sweet corn lines were determined to have a genetic basis. Significant quantitative variation included alterations in date of pollen shed and silk emergence, silk emergence relative to pollen shed, plant height, ear, and kernel characteristics. These results show genotypic differences in the extent of qualitative somaclonal variation, with some quantitative variation having possible applications for conventional corn breeding programs.